Hi,
On 07/08/14 13:58, Rob Jones wrote:
[snip]
On a related subject, Having looked at a few uses of seq_file, I must
say that some users seem to make assumptions about the internal
workings of the module. Dangerous behaviour as only some behaviours are
documented.
e.g. The behaviour that "struct seq_file" pointer is stored in
file->private_data is documented and can therefore be relied upon but
the fact that the output buffer and its size are only defined at the
first output (and can therefore be pre-defined and pre-allocated by
user code) is not documented and could therefore change without warning.
This second behaviour is assumed in, for example, module fs/gfs2/glock.c
which could, therefore, stop working properly without warning if the
internal behaviour was changed.
While it is undocumented, it is I understand, how this feature was
intended to be used, so I think that it is safe to do this in the GFS2
case. Here is a ref to the thread which explains how it landed up like that:
https://www.redhat.com/archives/cluster-devel/2012-June/msg00000.html
Steve.
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